Question

How many grams of NaOH (MW = 40.0) are there in 500.0 mL of a 0.175 M NaOH solution?

Answer 1

Given Molarity of NaOH solution , M = 0.175 M

Volume of the solution , V = 500.0 mL

                                         = 500.0mL x ( 1/1000) (L/mL)

                                         = 0.5 L

We know that Molarity , M = number of moles of NaOH / volume of solution in L

From this number of moles of NaOH , n = Molarity x volume in L

                                                                = 0.175 M x 0.5 L

                                                                = 0.0875 mol

Number of moles , n = mass/ molar mass

So mass of NaOH present , m = number of moles x molar mass

                                                 = 0.0875 mol x 40.0 (g/mol)

                                                = 3.5 g

Therefore the mass of NaOH is 3.5g